This application claims priority under 35 USC §119 to Korean Patent Application No. 10-2008-0083464, filed on Aug. 26, 2008 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates generally to image sensors, and more particularly, to an image sensor having different types of color filters.
2. Background of the Invention
An image sensor transforms images into electrical signals. Recent advances in computer and communication industries demand high performance image sensors in various consumer electronic devices including digital cameras, camcorders, PCS (Personal Communication Systems), game devices, security cameras, and medical micro cameras.
A MOS (metal oxide semiconductor) image sensor is driven easily using various scanning methods. Also, a digital signal processing circuit is integrated into a single chip of the MOS image sensor for minimized product size. In addition, MOS process technology is used for fabrication of the MOS image sensor for reduced manufacturing cost. Furthermore, the MOS image sensor has low power consumption for application in battery-powered products. Accordingly, use of MOS image sensors has been rapidly increasing with advances in implementation of high resolution MOS image sensors.
A MOS image sensor is typically divided into two regions: a sensor array region where multiple unit pixels are formed, and a surrounding peripheral circuit region where circuits to control/drive the multiple unit pixels are formed. The sensor array region includes multiple photoelectric conversion devices and multiple MOS transistors, and the surrounding circuit region includes multiple MOS transistors forming the circuits.
The sensor array region and the surrounding circuit region are integrated on one substrate, and the transistors formed in the sensor array region and the surrounding circuit region are formed simultaneously. Also, for increasing condensing efficiency, multiple lenses are formed for respective multiple photoelectric conversion devices. Furthermore, a protection layer composed of LTO (Low Temperature Oxide) is typically formed on the multiple lenses.
When a MOS image sensor includes a green color filter composed of organic material, a transmittance of less than 90% has been measured for the green color filter transmitting light near a wavelength of 550 nm. Such low transmittance degrades the optical characteristics of the image sensor in a spectral transmittance graph with loss of incident light reaching the photoelectric conversion element. Thus, the optical characteristics of the image sensor are deteriorated in that case.